The price
Every suite and every app has an organisation price per month that covers 3 users, and a per-user price for each person beyond that. A suite is always cheaper than its apps bought one by one; All suites is cheaper than the three suites.
Monthly
You are billed by the day. Start an app on the 13th and the first invoice covers the 13th to the end of that month; from then on a full month at a time. One GST invoice for the organisation arrives between the 1st and 5th of each month and is collected by autopay.
Yearly
Pay twelve months up front minus the yearly discount shown on Pricing. The year is counted from the day your first trial began. It renews yearly; you can switch back to monthly at renewal.
Users
Add people freely. The invoice counts the users on the account at the end of the month.
Where to see it
Account → Plans & Billing shows every app and suite, what is on trial, what is paid, the next invoice and every past one.